The present invention generally relates to power save mode control methods and storage units, and more particularly to a power save mode control method for controlling a power save mode of a storage unit which supports recording mediums having different formats, and to a storage unit which employs such a power save mode control method.
In this specification, the recording mediums having different formats include recording mediums having different storage capacities.
In disk units which support optical disks, magneto-optic disks and the like, an operation mode switches to a power save mode when an operating instruction from a host unit is not received for a predetermined time, so as to reduce the power consumption. In the power save mode, a part of the disk unit is stopped. For this reason, when restoring the operation mode from the power save mode to a read/write mode or the like, it is desirable to quickly restore the stopped part of the disk unit to the operating state.
An optical disk unit, for example, is provided with a plurality of power save modes depending on the time for which no operating instruction is received from the host unit, and the power consumption of the optical disk unit is efficiently reduced. In one power save mode, clocks for setting a crystal oscillator and a synthesizer which are used to set a cutoff frequency of an automatic filter tuning (AFT) circuit within the optical disk unit are stopped. On the other hand, when restoring the operation mode of the optical disk unit from this one power save mode to the read/write mode, an initial sequence of a read circuit within the optical disk unit is carried out to set the clocks of the crystal oscillator and the synthesizer. Such an initial sequence of the read circuit is carried out regardless of the power save mode from which the operation mode of the optical disk unit is restored to the read/write mode.
First, in a case where an optical disk having a storage capacity of 640 MB is loaded into the optical disk unit in a state where the clocks of the crystal oscillator and the synthesizer are preset with respect to the optical disk having the storage capacity of 640 MB, the operation of restoring the operation mode of the optical disk unit from the power save mode to the read/write mode is carried out as follows. For the sake of convenience, it is assumed that the operation mode of the optical disk unit is the power save mode from a time t1, and that a read/write instruction is received from the host unit at a time t2.
From the time t2, the cutoff frequency of the AFT circuit described above is set based on the preset clocks of the crystal oscillator and the synthesizer. A read/write process is carried out from a time t3 to a time t4, where t1 less than t2 less than t3 less than t4. Accordingly, a restoration time required to restore the optical disk unit from the power save mode to the read/write mode corresponds to the time interval from the time t2 to the time t3.
The optical disks supported by the optical disk unit include optical disks having different formats. For this reason, the clocks of the crystal oscillator and the synthesizer within the optical disk unit must be set depending on the format of the optical disk loaded into the optical disk unit.
FIG. 1 is a time chart for explaining the operation of restoring the operation mode of the optical disk unit from the power save mode to the read/write mode according to the prior art in the case where an optical disk having a storage capacity of 230 MB is loaded into the optical disk unit in a state where the clocks of the crystal oscillator and the synthesizer are preset with respect to the optical disk having the storage capacity of 640 MB. In this case, it is necessary to carry out the initial sequence of the read circuit within the optical disk unit and to change the setting so that the clocks of the crystal oscillator and the synthesizer are set with respect to the optical disk having the storage capacity of 230 MB. In FIG. 1, the operation mode of the optical disk unit is the power save mode from the time t1, and the read/write instruction is received from the host unit at the time t2.
In this case, there is a possibility that the clocks of the crystal oscillator and the synthesizer are set with respect to the optical disk having the storage capacity of 230 MB. For this reason, the initial sequence of the read circuit within the optical disk unit is carried out from the time t2 shown in FIG. 1, to change the setting so that the clocks of the crystal oscillator and the synthesizer are set with respect to the optical disk having the storage capacity of 640 MB. From a time t2a, the cutoff frequency of the AFT circuit is set based on the clocks of the crystal oscillator and the synthesizer which are set with respect to the optical disk having the storage capacity of 640 MB. The cutoff frequency of the AFT circuit is set with respect to the optical disk having the storage capacity of 640 MB in this case regardless of the storage capacity of the optical disk which is loaded into the optical disk unit. Hence, it is necessary to set the clocks of the crystal oscillator and the synthesizer with respect to the optical disk having the storage capacity of 640 MB before setting the cutoff frequency of the AFT circuit. Furthermore, from a time t2b, the setting is changed to set the clocks of the crystal oscillator and the synthesizer with respect to the loaded optical disk having the storage capacity of 230 MB, and the read/write process is carried out from a time t3a to a time t4a. Accordingly, the restoration time required to restore the optical disk unit from the power save mode to the read/write mode corresponds to the time interval from the time t2 to the time t3a. 
As may be seen from FIG. 1, in the case where the optical disk having the storage capacity of 230 MB is loaded into the optical disk unit in the stage where the clocks of the crystal oscillator and the synthesizer are preset with respect to the optical disk having the storage capacity of 640 MB, the restoration time required to restore the optical disk unit from the power save mode to the read/write mode is a sum of a set time from the time t2 to the time t2a, a set time from the time t2a to the time t2b, and a set time from the time t2b to the time t3a. Particularly, the set time from the time t2 to the time t2a and the set time from the time t2b to the time t3a include an oscillation stabilizing wait time of approximately 50 ms, for example, which is required for the operation of the crystal oscillator to stabilize. Therefore, there was a problem in that the restoration time became long in the prior art.
Accordingly, it is a general object of the present invention to provide a novel and useful power save mode control method and storage unit, in which the problem described above is eliminated.
Another and more specific object of the present invention is to provide a power save mode control method and storage unit, which can shorten the restoration time required to restore the storage unit from a power save mode to another mode.
Still another object of the present invention is to provide a power save mode control method for a storage unit which is loadable with recording mediums having different formats, comprising the steps of detecting whether or not a format of a recording medium loaded into the storage unit is a first format which is preset, and setting a clock frequency of a clock within the storage unit to a first frequency with respect to the recording medium having the first format when changing a mode of the storage unit to a power save mode if the loaded recording medium has the first format. According to the power save mode control method of the present invention, it is possible to reduce the restoration time required to restore the mode of the storage unit from the power save mode to another mode. In addition, if the loaded recording medium has a second format different from the first format and the clock frequency is set to a second frequency which is for the second format and is different from the first frequency when changing the mode of the storage unit from the power save mode to a predetermined mode, the clock frequency is automatically set depending on the format of the loaded recording medium, thereby making it unnecessary for the user of the storage unit to be aware of the format of the recording medium which is loaded into the storage unit.
A further object of the present invention is to provide a power save mode control method for a storage unit which is loadable with recording mediums having different storage capacities, comprising the steps of detecting whether or not a storage capacity of a recording medium loaded into the storage unit is a first storage capacity which is preset, and setting a clock frequency of a clock within the storage unit to a first frequency with respect to the recording medium having the first storage capacity when changing a mode of the storage unit to a power save mode if the loaded recording medium has the first storage capacity. According to the power save mode control method of the present invention, it is possible to reduce the restoration time required to restore the mode of the storage unit from the power save mode to another mode. In addition, if the loaded recording medium has a second storage capacity different from the first storage capacity and the clock frequency is set to a second frequency which is for the second storage capacity and is different from the first frequency when changing the mode of the storage unit from the power save mode to a predetermined mode, the clock frequency is automatically set depending on the storage capacity of the loaded recording medium, thereby making it unnecessary for the user of the storage unit to be aware of the storage capacity of the recording medium which is loaded into the storage unit.
Another object of the present invention is to provide a storage unit loadable with recording mediums having different formats, comprising means for detecting whether or not a format of a recording medium loaded into the storage unit is a first format which is preset, and means for setting a clock frequency of a clock within the storage unit to a first frequency with respect to the recording medium having the first format when changing a mode of the storage unit to a power save mode if the loaded recording medium has the first format. According to the storage unit of the present invention, it is possible to reduce the restoration time required to restore the mode of the storage unit from the power save mode to another mode. In addition, if the loaded recording medium has a second format different from the first format and the clock frequency is set to a second frequency which is for the second format and is different from the first frequency when changing the mode of the storage unit from the power save mode to a predetermined mode, the clock frequency is automatically set depending on the format of the loaded recording medium, thereby making it unnecessary for the user of the storage unit to be aware of the format of the recording medium which is loaded into the storage unit.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.